Fifteen years after the attacks of Sept. 11, Americans have grown aware not only of the danger of terrorism but also of the reality that their nation is far less white, Christian and European than it used to be.

"Culturally, we're a country of Bollywood and bhangra and tai chi and yoga and salsa and burritos and halal and kosher," says Diana Eck, professor of comparative religion at Harvard University and author of A New Religious America.

Through her direction of the Pluralism Project at Harvard, Eck and her researchers have documented the growth of an "interfaith infrastructure" in the country.

"After 9/11," she says, "it became important to know more clearly who is in our community. The level of ignorance was cracked. It is far from solved, but I think 9/11 did bring a moment of awakening that the 'we' of the United States is changing."

A recognition of America's increased diversity is especially critical for the Muslim American community. The Sept. 11 attacks were carried out in the name of Islam, and a majority of Muslims in the United States have said it became harder after those attacks to be a Muslim in this country.

In response, many are taking the responsibility themselves for improving relations with their neighbors. One important consequence of Sept. 11 was that Muslims, most of whom are immigrants, concluded they needed to become more socially and politically engaged.

Interfaith efforts in those days were scorned as un-Islamic, he says. Bukhari, who moved from Pakistan to the U.S. in the 1980s and now lives in Frederick, Md., urges his fellow immigrant Muslims, including the most devout, to turn their attention away from their native lands and focus on their adopted homeland.

"God will not ask them, at the Day of Judgment, what they have done in Karachi or Lahore or Istanbul," Bukhari says. "God will ask me what I have done in Frederick, with my family, with my neighbors. Did I become a symbol of goodness or a symbol of badness?"

Part of this new engagement effort among immigrant Muslims has been to promote more civic participation.

"There were a lot of controversies whether we should take part in the political process," Bukhari says. "Was it halal [Islamically permissible] or haram [prohibited]? Now that debate is over."

The struggle to improve the image of Muslim Americans has not been easy. A 2014 survey by the Pew Research Center found that of eight major religious groups in the country, people ranked Muslims at the very bottom.

But Besheer Mohamed, one of the researchers on the report, says one conclusion was that the more interaction there is between Muslims, Christians and others, the better their relations.

"Muslims were rated the lowest, but people who say that they knew a Muslim personally rated Muslims significantly higher than people who said they didn't know Muslims," Mohamed says.

As a religion, however, Islam remains controversial in the United States. A separate Pew study found that the number of people who say Islam is more likely than other religions to encourage violence has grown in the past 15 years, and partisan differences over the issue have intensified, with Republican and Democratic views diverging widely.

A major rupture between Muslim Americans and the Republican Party appears to be another post-Sept. 11 development.

In the 2000 election, a survey by the Muslims in the American Public Square (MAPS) project at Georgetown University and Zogby Analytics found that immigrant Muslims, especially those from Arab countries, preferred George W. Bush, the Republican candidate, over Democrat Al Gore. They appreciated Bush's criticism of the racial profiling of Arab-Americans, and many aligned with conservative positions on social issues and the Republican emphasis on personal responsibility over government welfare.

After Sept. 11, however, immigrant Muslims overwhelmingly abandoned the Republican Party, with just 7 percent backing Bush's re-election in 2004. (African-American Muslims voted against Bush in large numbers in both elections.)

That trend is likely to continue this year, with Republican candidate Donald Trump on the record as saying "I think Islam hates us."

A survey earlier this year during the Republican and Democratic party primaries found that Trump had the lowest support of any candidate, favored by just 4 percent of Muslim voters.

While Muslims face the most suspicion in the United States, other religious minorities also encounter hostility. The Pew survey that placed Muslims at the bottom in public esteem found Buddhists and Hindus, two other immigrant faith groups, ranked lower than Christians and Jews.

"These are growing pains," says Harvard's Diana Eck. "There's no question that this moment in America is an especially painful one. [But] I have no doubt that the course of the United States as a multi-religious nation that is gradually coming to terms with its own diversity is one that will win out."

What is needed, Eck says, is for Americans to unite around the "common principles" that bind the nation.

"They are constitutional principles," Eck says. "They are principles that have to do with a sort of ethos, a cultural ethos of neighborliness."

"Diversity is a given," she says. "These [immigrant] movements are not things that are somehow going to be stopped and everyone sent home. This is part of the natural evolution of who we are as America."

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STEVE INSKEEP, HOST:

Every year this happens - at least to me. The anniversary of 9/11 approaches. You think it's finally been long enough that the day won't affect you that much. And then the day arrives, and it does. The country has changed as we approach the 15th anniversary, and that includes a change in our national religious identity. Here's NPR's Tom Gjelten.

TOM GJELTEN, BYLINE: The United States was changing before 9/11 with immigrants already arriving from distant lands in record numbers. At the Harvard Divinity School, Diana Eck had just published a book titled "A New Religious America: How A Christian Country Has Become The World's Most Religiously Diverse Nation." The changes she highlighted then have continued.

DIANA ECK: Culturally, we are a country of Bollywood and bhangra and tai chi and yoga and salsas and burritos and halal and kosher.

GJELTEN: Growing diversity presents a challenge for our country. America's motto is e pluribus unum - out of many, one. But when there's so much pluribus, what's the unum? Professor Eck says it's a commitment to common principles.

ECK: Then we have those common principles in the United States. They're constitutional principles. They're principles that have more to do with a sort of ethos, a cultural ethos of neighborliness, for example.

GJELTEN: But 9/11 challenged that ethos. The attacks were carried out by Muslims in the name of Islam, and their image has suffered. When the Pew Research Center asked Americans two years ago to rank eight major religious groups, Muslims came in at the very bottom. And Muslim Americans feel it. A majority have said after 9/11 it became harder to be a Muslim in this country. But the lesson that immigrant Muslims in particular took from that is that they needed to become more engaged in America, socially, politically and mentally.

ZAHID BUKHARI: Before September 11, Muslims were - the majority of them, they were living here physically. Mentally, spiritually, they were living back home.

GJELTEN: Zahid Bukhari came from Pakistan in the '80s. He now lives in Frederick, Md. He's held high office in several Muslim organizations and always urges his fellow Muslims, including the most devout, to keep their focus here, like he now does.

BUKHARI: God will not ask them at the day of judgment what they have done in Karachi or Lahore or Istanbul. God will ask me what I have done in Frederick with my family, with my neighbors. Did I become a symbol of goodness or a symbol of badness?

GJELTEN: It does seem the more interaction there is between people of different backgrounds the better their relations. Besheer Mohamed directed that Pew study of Americans' attitudes toward religious minorities.

BESHEER MOHAMED: People who said that they knew a Muslim personally rated Muslims significantly higher than people who said they didn't know Muslims.

GJELTEN: Since 9/11, interfaith efforts in America have expanded, but Islam still has an image problem. Pew researchers have found that the number of people who think Islam encourages violence has grown during the last 15 years. Another change - feelings about Muslims and Islam have become much more partisan in this time. Zahid Bukhari was one of the researchers behind a study of how Muslim Americans voted in the 2000 election.

BUKHARI: Among immigrant Muslims, they supported George Bush because George Bush at that time spoke very much in favor of Arabs.

GJELTEN: And it wasn't just what Bush said about Arabs. Many Muslim Americans liked conservative Republican positions on social issues. But in the years since 9/11, Muslim Americans have almost entirely abandoned the Republican Party, driven away in part by what they hear from Republican politicians.

(SOUNDBITE OF ARCHIVED RECORDING)

DONALD TRUMP: I think Islam hates us.

GJELTEN: Donald Trump speaking to CNN's Anderson Cooper last March.

(SOUNDBITE OF ARCHIVED RECORDING)

TRUMP: There's something there that's a tremendous hatred.

GJELTEN: Besides Muslims, Hindus and Buddhists here are held in relatively lower esteem than Christians and Jews. It's these recent immigrant faith traditions that are struggling to gain acceptance. But 15 years after 9/11, Americans know their country is less white and less Christian than it used to be.

ECK: These movements are not things that are going somehow to be stopped and everyone's going to be sent home. This is part of the natural evolution of who we are as America.

GJELTEN: Diana Eck of Harvard where she teaches comparative religion and reminds us that diversity is now our destiny. Tom Gjelten, NPR News. Transcript provided by NPR, Copyright NPR.

Women in colorful scarves, men, and children waved American flags on the lawn of the Dr. Phillips Center for Performing Arts in downtown Orlando, just feet away from a memorial to the victims of the Pulse nightclub shooting, chanting “Not in my name,” a direct message to extremist group the Islamic State to stop orchestrating terrorist acts in the name of Islam.

In an election year filled with anti-Muslim vitriol, some mosques are urging their worshipers to vote in an attempt to make their voices heard. To do so, they're borrowing a strategy used by African-American churches and organizing "souls to the polls" campaigns.

It is as if mainstream American media thrust LGBT Muslims into the spotlight overnight—all in the context of the man behind the shootings at Pulse, Omar Mateen.

“The Orlando massacre shooter led a startling secret life and may have been a closeted gay man,” anchors announced in front of cameras, reporting an television interview between Univision and a man in disguise named Miguel who claimed to have had a two-month sexual relationship with Mateen.